Gross anatomy

The transversus thoracis is a thin band of muscle and tendon arising from the lower posterior surface of the sternum, posterior edge of the xiphisternum and the costal cartilage of the lowest 3 - 4 ribs at their sternal end. It diverges supero-laterally to attach by slips to the underside of the 2nd to 6th costal cartilages1. The transversus thoracis muscle is morphologically identical to the transversus abdominis muscle 2.